Field of the Invention
Embodiments presented in this disclosure generally relate to generating electrical power. More specifically, embodiments disclosed herein reduce common mode current generated when using interleaved switching.
Description of the Related Art
In variable speed generators, a frequency converter is used to convert power from the generator at variable frequency to a predefined frequency corresponding to a load—e.g., a utility grid. In one example, the frequency converter converts the AC signal provided by the generator to a DC signal and then back to an AC signal with a frequency that matches the desired frequency of the load. To convert the DC signal to an AC signal with the desired frequency, the frequency converter may use pulse width modulation (PWM) based on a switching frequency. However, in frequency converters where the switching frequency is much higher than the frequency of the generator signal, PWM introduces a high-frequency ripple onto the desired AC signal which may require expensive (and bulky) filtering components to remove before the signal is suitable for a utility grid.
Performing interleaved PWM switching may be preferred since doing so reduces the high-frequency ripple, and thus, reduces the cost and size of the filtering components. However, even with interleaved switching, the frequency converter may output an AC signal with a high-frequency ripple, and thus, filtering components such as the choke may still be required. As such, there is need for additional techniques that can reduce the size and complexity of the filtering components which may reduce the cost of the power generation system.